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Irish Surnames


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This list contains many of the most common Irish surnames found in the United States and also their root derivations. Like most Western names, many of these are based upon an ancestor's occupation or appearance or place of residence.

The prefixes of "O'", "Mc", and "Mac" are common in Irish surnames. These are all references to ancestry.

Mac is the Gaelic word for son. It is now often abbreviated to "Mc", but originally it was the longer word and normally followed by a space and then the surname. There is a tradition that Mac is Irish and Mc is Scottish, but this is false. Both variations are in wide use in both countries.

O is really a word all by itself, it means "grandson". Only in recent years has it been attached to the surname with an apostrophe.

In ancient Ireland, there were no fixed surnames. A man was known as the the "son of" his father's first name. Occaisionally a man would be known by his grandfather's name (by the word O) if his grandfather was especially noteworthy. Around the twelfth century, most all of Europe and England adopted standardized surnames. Irish families did the same.

The other distinctively Irish prefix is Fitz, as in Fitzgerald or FitzAlan. This is a Norman French prefix, brought to Ireland by the Normans who previously had lived in England. It is derived from the French word fils, meaning "son of". Therefore, Fitz and Mac mean about the same and were interchangeable at one time.

It is now common for the O and Mac prefixes to be eliminated entirely.

The original Celtic words are listed in parentheses.

  • Barry - from the Norman French surname de Barri
  • Brennan - O Braonain, descendant of Braonain (a word for "sorrow")
  • Burke - from the Norman French surname de Burgh or de Bourg
  • Byrne - O Broin, descendant of Broin (bran means "raven")
  • Casey - O Cathasaigh, descendant of Cathasaigh (cathasach means "watchful")
  • Daly - O Dalaigh, descendant of Dalaigh (dalach means "assemblyman")
  • Donohue - O Donnchadha, descendant of Donnchadha (donn means "brown haired")
  • Dunne - O Duinne, a descendant of Duinn (donn means "brown" or "brown haired"
  • Fitzgerald - son of Gerald (a Norman French name)
  • Fitzpatrick - This name was originally Mac Giolla Padraig, meaning a descendant of a devotee of St. Patrick. In later years the Mac prefix was changed to the Norman "Fitz".
  • Flynn - O Floinn, descendant of Floinn (flann, meaning "ruddy")
  • Kelly - O Ceallaigh, descendant of Ceallaigh (ceallach is the word for "strife"
  • Kennedy - O Cinneide, descendant of Cinneide (ceann means "head", eidigh means "ugly")
  • Lynch - from the Norman French surname de Lench
  • McCarthy - Mac Carthaigh, descendant of Carthaigh (carthach means "loving")
  • Murphy - O Murchadha, descendant of a murchadh (sea warrior)
  • O'Brien - O Briain, descendant of Briain (Brian Boru)
  • O'Connor - O Conchobhair, descendant of Conchobhair
  • O'Donnell - O Domhnaill, descendant of Domhnaill
  • O'Neill - O Neill, descendant of Neill ("Neill of the Nine Hostages")
  • Quinn - O Cuinn, descendant of Conn
  • Regan - O Riagain, descendant of Riagain
  • Reilly - O Ragailligh, descendant of Ragaillach
  • Ryan - O Malvilriain, descendant of Mavilriain (a name not identifiable)
  • Sullivan - O Suileabhain, descendant of Suileabhain (suil means "eye" and Levan is a Celtic deity. Therefore, this is the "eye of the god")
  • Walsh - a person of Welsh origin

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